Explicitly listing umountfs and umountroot for remove in sysvinit script to be on the conservative side, instead of using 'umount*' pattern to match them.

When doing LXC things we need to be extra cautious, better to need to
update the harcoded list (and thus relying on getting updates to the
users to update them for newer sysvinit versions) rather than to need
the update to prevent errors (and thus not relying on getting updates
to the users to fix their systems).